GB1527754A - Indexing mechanisms - Google Patents

Abstract

1527754 Toothed gearing J H BREMS 25 Sept 1975 [26 Sept 1974] 39233/75 Heading F2Q In an intermittent rotary drive mechanism a continuously-rotated input shaft 104 on a fixed axis A1 is coupled by sprockets 122, 118 and chain 120 to a shaft 112 of movable axis A2, located relatively to A1 by a radius arm 106, while a spur gear 126, together with its stub shaft 128, is fixedly secured to the shaft 112 upon an eccentric axis A3, and at the same time the input shaft 104 carries a spur gear 152 meshed with a gear 154 on a fixed shaft 156, thereby driving a cam 160, from which a cam follower 162 derives a cyclic motion between two levels of cam contour, with this motion linked to provide angular motion of a cranked arm 144, of which a portion 142 carries an arcuate recess 140 engaged upon the stub shaft 128, and causing the spur gear 126 to be drawn alternately into mesh and out of mesh with an output gear 130 on a fixed axis A4. The pitch circle radius of gear 126 is approximately equal to the spacing between axes A2 and A3, and with the locus of axis A2 constrained by arm 106, and the spacing between axes A3 and A4 set by arm 144, the sprocket 118 and gear 126 perform a gyrating movement with the axes A2 and A3 revolving about each other. During periods when gears 126 and 130 are meshed together, the resulting motion of the output gear 130 is one of cyclically varying angular velocity, with a brief stationary dwell period once during each basic cycle comprising one revolution of shaft 112. The gear ratios and the configuration of cam 160 are chosen such that gear 126 is transferred into mesh and out of mesh with gear 130 only during dwell periods thereby providing a means for imposing an extension of the dwell period, to embrace one or more entire basic cycles. During these periods, while gear 126 continues to revolve out of mesh, gear 130 may be held stationary by a toothed segment 150, engaged by the arm 144. In another embodiment, a spur wheel on axis A3 engages an internal ring gear forming the output wheel, and a stub shaft on axis A3 acts directly as a cam follower, engaged in a facial cam slot of a cam wheel mounted coaxially upon the output wheel axis A4. In a further embodiment, chains constantly engaged upon sprockets are used in place of spur gears, and the output drive becomes disengaged by the withdrawal of an eccentrically disposed key pin, actuated by a facial cam.